“Canola”, refers to a particular class of rapeseed (Brassica napus oleifera annua) having: (i) a seed oil that contains less than 2% erucic acid, and (ii) an oil-free meal that contains less than 30 micromoles aliphatic glucosinolates per gram of meal. Canola seed can be extracted or pressed for cooking oil and the residual meal is used as an organic fertilizer and as a high-protein animal feed supplement. Industrial uses of canola include biodiesel and plastic feedstocks.
Farmers in Canada began producing canola oil in 1968. Early canola cultivars were known as single zero cultivars because their oil contained 5% or less erucic acid, but the glucosinolates content was still higher than desired. In 1974, the first licensed double zero cultivars (low erucic acid and low glucosinolates) were grown. All current canola cultivars are double zero cultivars.
Because the fatty acid profile of canola oil is generally viewed as “healthy”, its use is rising steadily both as an oil for cooking and as an ingredient in processed foods. It is generally lower in saturated fatty acids and high in monounsaturated fatty acids than other seed oils. In addition, many people prefer the light color and mild taste of canola oil over other oils that contain monounsaturated fatty acids.
The goal of a canola breeder is to develop new, unique, and superior canola cultivars having improved desirable traits. Improved performance is manifested in many ways. Higher yields of canola plants contribute to higher seed production per acre, a more profitable agriculture and a lower cost of products for the consumer. Improved oil profiles and quality of resulting oil is an important factor in the development of new canola cultivars. Adapting canola plants to a wider range of production areas achieves improved yield and vegetative growth. Improved plant uniformity enhances the farmer's ability to mechanically harvest canola. Improved nutritional quality increases its value in food and feed.
The development of new cultivars in a canola plant breeding program involves numerous steps, including: (1) selection of parent canola plants for the initial breeding crosses; (2) producing and selecting inbred breeding lines and cultivars by either the doubled-haploid method or repeated generations of selfing individual plants; (3) producing and selecting hybrid cultivars by crossing a selected inbred male-sterile line with an unrelated inbred restorer line to produce the F1 hybrid progeny having restored vigor; and (4) thoroughly testing these advanced inbreds and hybrids compared to appropriate standards for three or more years in environments representative of the commercial target areas.
Development and selection of new canola parental lines, the crossing of these parental lines, and selection of superior hybrid progeny are vital to maintaining a canola breeding program. The F1 hybrid canola seed is produced by manual crosses between selected male-fertile parents or by using male-sterility systems. These hybrids are selected for certain single-gene or multiple gene traits. Additional data on parental lines, as well as the phenotype of the hybrid, influence the breeder's decision whether to continue with the specific hybrid cross.
The method of doubled-haploid breeding consists of donor selection, microspore culture and chromosome doubling, embryo cold stress, plantlet regeneration, ploidy analysis, and self-pollination to produce seed of doubled-haploid lines. The advantage of the doubled-haploid method is that the time to develop a new completely homozygous and homogeneous cultivar can be reduced by 3 years compared to the conventional inbreeding method of multiple generations of self-pollination.
These processes, which lead to the final step of marketing and distribution of a cultivar, usually take from 8 to 12 years from the time the parental cross is made. Therefore, development of new canola inbred and hybrid cultivars is a slow, costly process that requires the resources and expertise of plant breeders and numerous other specialists.
It is nearly impossible for two canola breeders to independently develop genetically-identical canola inbreds or hybrids expressing all the same trait characteristics. The cultivars that are developed cannot be predicted because the breeder's selection occurs in unique environments, with no control over meiotic genetic recombination (using conventional breeding procedures), and with millions of different possible genetic combinations possible. A breeder of ordinary skill in the art cannot predict the final resulting lines he/she develops, except possibly in a very gross and general fashion. It is unlikely a breeder could produce the same cultivar twice by using the exact same original parents and the same selection techniques.
Canola cultivars and other sources of canola germplasm are the foundation material for all canola breeding programs. Despite the existence and availability of numerous canola cultivars and other source germplasm, a need still exists for the development of improved germplasm to improve and maximize yield and oil quality.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification.